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Countersinks are used to prepare the rims of drilled holes to fit countersunk screws or to deburr drilled holes. Depending on material, workpiece shape and application, the following types are used:

Tapered countersink

Tapered countersinks have a conical tip and three or more cutters. Their point angles are 60, 75, 90 or 120 degrees. As a rule, the shank diameter is smaller than the head diameter. The number of cutters is always uneven to avoid rattling during operation. Countersinks with three cutters and large flutes are used for deep countersinking. Countersinks with 5 or more cutters are used for flat countersinking.

Countersink with slanted hole

Countersinks with slanted holes have a conical cutter head with a slanted opening. The cutting edge is formed by the slanted opening on the cutter head. Due to the special cutting edge geometry, even long filings can escape in a continuous flow which allows rattle-free countersinking especially in thin metal sheets.

Plug-on countersink

Plug-on countersinks are similar to tapered countersinks. However, instead of a shank, they possess a bore to fit a standard twist drill bit. The plug-on countersink is fixed on the drill bit at the desired distance from the tip and allows simultaneous drilling and countersinking in wood.

If the plug-on countersink is reversed, it serves as a depth stop when drilling blind holes.